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Two weeks ago a technician came to our house (in Broken Arrow, Oklahoma) for our semi-annual "Energy Savings Agreement" service call. I have been very satisfied using this same company for over 20 years. This call was to service the furnaces. Our gas furnaces are Goodman, GMP100-4-RevB and GMP050-3-RevB. Included in the work performed was the following for both units:

I hadn't thought anything of the work performed until yesterday when I read some disturbing information on this forum regarding adjusting gas pressure. Is a gas pressure adjustment to 3.5 safe or should I be concerned?

dittos

Yes, read the rating plate as 3.5 inches of water column (abbreviated w.c. or wci) is the most common. This tech gets a cookie. So it also begs the question: what the heck has everyone else been doing for the last 20 yrs? Apparently, this unit has been overfiring since it was installed. The unit could be damaged. Did he test for heat exchanger cracks, CO leakage, and do a combustion analysis? Don't celebrate too soon. This unit should have been set properly at installation. Now, you have a big question about its longevity.

FYI, this is just the manifold or burner pressure. You also have to be concerned with the inlet pressure under load.

dittos

Yes, read the rating plate as 3.5 inches of water column (abbreviated w.c. or wci) is the most common. This tech gets a cookie. So it also begs the question: what the heck has everyone else been doing for the last 20 yrs? Apparently, this unit could have been overfiring or underfiring since it was installed. The unit could be damaged. Did he test for heat exchanger cracks, CO leakage, and do a combustion analysis? Don't celebrate too soon. This unit should have been set properly at installation. Now, you have a big question about its longevity.

FYI, this is just the manifold or burner pressure. You also have to be concerned with the inlet pressure under load.

Did he adjust it up or down? Why was it out of adjustment it the first place? Yeah, great job in checking the pressure but if there is an obstruction in the orfices than when it becomes dislodge, could have more problems. Should have check orfices before adjusting inlet pressure. Just my opinion.

I'm sorry if I mislead anyone. I've been using the same HVAC company for 20 years. However, that service history covers three different houses. My current furnaces are only four years old and were installed during construction of my current house (June 2001), and were not installed by my longstanding service company.

I'm not sure whether the technician adjusted the gas pressure up or down, or by how much. He made a comment about the high cost of gas, so I assumed he adjusted the pressure slightly downward. Since the units performed well over the previous four winters, I'm sure it was only a minor adjustment. I inspected the rating plate on each unit last night and they both show a manifold pressure rating of 3.5.

I want to thank everyone who responded for his or her information, advice and concern. I feel confident that my furnaces are operating properly and have not sustained any potentially long term damage.